From b8da7a046d3ec13974004291b100b4bfc80db836 Mon Sep 17 00:00:00 2001
From: Mike Stump <mrs@apple.com>
Date: Thu, 5 Nov 2009 06:12:26 +0000
Subject: [PATCH] Refine covariant return value adjustments for thunks when
 null pointers are returned.

llvm-svn: 86120
---
 clang/lib/CodeGen/CGCXX.cpp    | 20 +++++++++++++++++++-
 clang/test/CodeGenCXX/virt.cpp |  6 +++++-
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/clang/lib/CodeGen/CGCXX.cpp b/clang/lib/CodeGen/CGCXX.cpp
index d4adbad1e45e..fd90dc06d505 100644
--- a/clang/lib/CodeGen/CGCXX.cpp
+++ b/clang/lib/CodeGen/CGCXX.cpp
@@ -811,7 +811,25 @@ llvm::Constant *CodeGenFunction::GenerateCovariantThunk(llvm::Function *Fn,
                        Callee, CallArgs, MD);
   if (nv_r || v_r) {
     // Do the return result adjustment.
-    RV = RValue::get(DynamicTypeAdjust(RV.getScalarVal(), nv_r, v_r));
+    llvm::BasicBlock *NonZeroBlock = createBasicBlock();
+    llvm::BasicBlock *ZeroBlock = createBasicBlock();
+    llvm::BasicBlock *ContBlock = createBasicBlock();
+
+    const llvm::Type *Ty = RV.getScalarVal()->getType();
+    llvm::Value *Zero = llvm::Constant::getNullValue(Ty);
+    Builder.CreateCondBr(Builder.CreateICmpNE(RV.getScalarVal(), Zero),
+                         NonZeroBlock, ZeroBlock);
+    EmitBlock(NonZeroBlock);
+    llvm::Value *NZ = DynamicTypeAdjust(RV.getScalarVal(), nv_r, v_r);
+    EmitBranch(ContBlock);
+    EmitBlock(ZeroBlock);
+    llvm::Value *Z = RV.getScalarVal();
+    EmitBlock(ContBlock);
+    llvm::PHINode *RVOrZero = Builder.CreatePHI(Ty);
+    RVOrZero->reserveOperandSpace(2);
+    RVOrZero->addIncoming(NZ, NonZeroBlock);
+    RVOrZero->addIncoming(Z, ZeroBlock);
+    RV = RValue::get(RVOrZero);
   }
 
   if (!ResultType->isVoidType())
diff --git a/clang/test/CodeGenCXX/virt.cpp b/clang/test/CodeGenCXX/virt.cpp
index a85b2dfe477e..193a96ddd589 100644
--- a/clang/test/CodeGenCXX/virt.cpp
+++ b/clang/test/CodeGenCXX/virt.cpp
@@ -1076,12 +1076,16 @@ void test16_D::bar() { }
 // CHECK-LPOPT64-NEXT:    subq    $8, %rsp
 // CHECK-LPOPT64-NEXT:Llabel
 // CHECK-LPOPT64-NEXT:    call    __ZN8test16_D4foo1Ev
-// FIXME: We need a == 0 check here
+// CHECK-LPOPT64-NEXT:    testq   %rax, %rax
+// CHECK-LPOPT64-NEXT:    je      LBB102_2
 // CHECK-LPOPT64-NEXT:    movq    16(%rax), %rcx
 // CHECK-LPOPT64-NEXT:    movq    -32(%rcx), %rcx
 // CHECK-LPOPT64-NEXT:    leaq    16(%rcx,%rax), %rax
 // CHECK-LPOPT64-NEXT:    addq    $8, %rsp
 // CHECK-LPOPT64-NEXT:    ret
+// CHECK-LPOPT64-NEXT:LBB102_2:
+// CHECK-LPOPT64-NEXT:    addq    $8, %rsp
+// CHECK-LPOPT64-NEXT:    ret
 
 
 class test17_B1 {
-- 
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